Some nutrients, and vitamins in particular, are soluble in water. They tend to migrate towards this medium if we immerse them in it: we say that they are water-soluble. If you cook the vegetables in water, some of the nutrients will be lost in the cooking water.

The example of broccoli, rich in vitamin C, is very telling: cooking in water causes them to lose more than 30% of their vitamin C content, steam cooking almost 20% and preparation in the oven in the oven. microwave brings it down to below 10%!

A study¹succeeded in showing that cooking in water led to greater losses in leafy vegetables (63% potassium, 59% Sodium and 43% Magnesium) than steam cooking (17% potassium, 17 % Sodium and 11% Magnesium).

Steam cooking to be preferred

On a daily basis, therefore, steam cooking is ideal, but stewing is also possible. This is done in a closed container (a covered saucepan for example) over very low heat and using only the water contained in the food.

During cooking, the perimeter of the food suffers the most damage. In the heart, the nutritional changes are less marked because the temperature is often lower there. By ensuring homogeneous heat (and by maintaining a temperature that never exceeds 100 ° C), steaming makes it possible to limit the destruction of vitamins and the formation of toxic compounds since it takes less time to cook the heart of the vegetables. food. Cooking in foil, which involves placing food in an airtight container and placing everything in the oven, boiling water or microwave, is a popular method. The best product for the papillote remains the parchment paper, and not the aluminum which can contaminate the food. In addition, the electric steamer (with, ideally, a “vitamin” function) is an interesting and very practical possibility, unlike the pressure cooker which denatures nutrients: the increase in pressure that it allows makes raise the temperature above 100 ° C!

Varying the cooking: the best solution?

If steam cooking has quite a good press when it comes to its health benefits, this is not really the case when it comes to the taste of food. Unlike other cooking techniques (grilling or sautéing for example), steam does not allow caramelization and the appearance of these succulent compounds that are the bodies of Maillard. They correspond to the action of sugars on proteins at high temperature, and are notably responsible for the characteristic taste of grilled meats. The right balance between vitamin content and taste may be found on the side of the steam oven, even if the latter, bulky and very expensive, is not yet an affordable choice for everyone.

Raw, boiled, sautéed, braised … Finally, the variety of cooking is probably the best guarantee to succeed in juggling between pleasure and quality nutrition!

What about cooking with water?

If you opt for cooking with water (useful in particular for cooking large quantities of vegetables), collect the cooking water, which is very rich in nutrients, to flavor soups, sauces or broths. It is best to use enough water so that it boils again quickly after adding the vegetables. These would benefit from being roughly cut (the surface in contact with the water being smaller) to limit the loss of nutrients: a cleaner cut is always possible after cooking.

Trick : Immerse the vegetables in ice water to stop the cooking and thus stop the nutritional loss which continues off the heat. Be careful, however, not to soak them!

Sources: Sources: Causeret, 1986 The right choice for cooking: the healthiest cooking, the safest utensils, Juliette Pouyat